This invention relates to composites, e.g., coated products, laminates and/or combinations thereof, of the type incorporating fluoroplastics as barrier components. Typical applications for such composites include high temperature expansion joints in power plants and chemical processing installations, chemical tank covers, bladders and liners, high temperature insulation jacketing, protective clothing, etc.
In the past, suitable fluoroplastic materials for such composites have included polytetrafluoroethylene ("PTFE"), fluorinated ethylene propylene ("FEP"), and perfluoralkoxy ("PFA"). Although these materials exhibit excellent chemical resistance and barrier properties, they lack toughness (as herein employed, the term "toughness" means the ability of a material to resist multi-directional tearing). In prior applications, therefore, it has been deemed necessary by those skilled in the art to combine these materials with reinforcing substrates. Typically, the reinforcing substrates comprise non-fluoroplastics such as woven fiberglass to which the fluoroplastics are applied as coatings and/or as film laminates.
Although the non-fluoroplastic substrates supply the requisite toughness to the resulting composites, they do so with attendant drawbacks which have heretofore been recognized but considered unavoidable. For example, the non-fluoroplastic substrates contribute undesirable stiffness, bulk and weight to the composites. Non-fluoroplastics also resist stretching, which is desirable in many applications. Of greater concern, however, is the vulnerability of the non-fluoroplastic substrates to chemical attack and degradation. Theoretically, the substrates should be safeguarded from chemical attack by the fluoroplastic components of the composites. As a practical matter, however, chemical protection of the substrates is frequently compromised, typically as a result of the fluoroplastic components being inadvertently damaged through mishandling or unavoidably ruptured by fasteners such as screws, rivets, staples or the like when the composites are fabricated into various structures. Once the barrier properties of the fluoroplastic components are compromised, the non-fluoroplastic substrates are exposed to chemical attack and the composites are doomed to failure.
All-fluoroplastic composites including fabrics woven from fluoroplastic fibers combined with fluoroplastic coatings and/or films also have been developed. However, such composites have relatively low tensile and tear strengths, are relatively expensive to produce, and thus are appropriate for only a limited range of applications.
Accordingly, an objective of this invention is to provide a novel and improved PTFE laminate having high tensile and tear strengths, flexibility, and excellent chemical resistance and barrier properties.
A companion objective of the present invention is the provision of a relatively light weight PTFE laminate suitable for applications requiring toughness, chemical resistance and flexibility.
Still another objective of the present invention is the provision of a novel and cost effective method of producing the laminates of the present invention.